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Summary of Significant Accounting Policies - Additional Information (Detail) $ / shares in Units, $ in Millions |  | 1 Months Ended | 3 Months Ended |  |
--- | --- | --- | --- | --- | ---
Feb. 28, 2020 $ / shares shares | Dec. 31, 2020 shares | Dec. 31, 2020 USD ($) shares | Sep. 30, 2020 shares | Jun. 05, 2020 shares
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |
Capital stock authorized (in shares) | 2,100,000,000 |  |  |  |
Preferred stock authorized (in shares) | 100,000,000 |  |  |  |
Preferred stock par value (in dollars per share) | $ / shares | $ 1.00 |  |  |  |
Stock split, conversion ratio | 477,242.614671815 |  |  |  |
Preferred stock outstanding (in shares) |  | 0 | 0 |  | 0
Stock-based compensation expense | $ |  |  | $ 6 |  |
Restricted Stock Units (RSUs) |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |
Shares issued under Omnibus Incentive Plan (in shares) |  |  | 30,914 |  |
Restricted Stock Units (RSUs) | Omnibus Incentive Plan |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |
Shares issued under Omnibus Incentive Plan (in shares) |  |  | 2,553 |  |
Class A Common Stock |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |
Common stock authorized (in shares) | 1,000,000,000 | 1,000,000,000 | 1,000,000,000 | 1,000,000,000 |
Common stock outstanding (in shares) |  | 111,167,356 | 111,167,356 | 88,578,361 |
Shares issued in period (in shares) |  | 22,586,442 | 4,321,259 |  |
Class A Common Stock | Omnibus Incentive Plan |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |
Common stock available for issuance (in shares) |  | 31,169,099 | 31,169,099 |  |
Incentive plan period |  |  | 10 years |  |
Class A Common Stock | IPO |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |
Common stock outstanding (in shares) |  | 88,550,000 | 88,550,000 |  | 88,550,000
Class A Common Stock | IPO | Omnibus Incentive Plan |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |
Common stock available for issuance (in shares) |  | 1,000,000 | 1,000,000 |  |
Class B Common Stock |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |
Common stock authorized (in shares) | 1,000,000,000 | 1,000,000,000 | 1,000,000,000 | 1,000,000,000 |
Common stock outstanding (in shares) | 510,000,000 | 403,184,814 | 403,184,814 | 421,450,000 |
Exchange of LLC Units for Class B shares (in shares) |  |  | 18,265,813 |  |
Class B Common Stock | IPO |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |
Common stock outstanding (in shares) |  | 421,450,000 | 421,450,000 |  | 421,450,000

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